Tear-open seal packaging

ABSTRACT

The invention relates to a tear-open seal packaging ( 10 ), with a packaging element ( 12 ) having an opening ( 30 ) and a tear-open film ( 14 ), which closes opening ( 30 ) and is connected along its outer edge portion ( 16 ) with the opening edge ( 32 ) of packaging element ( 12 ) by a sealing seam ( 18 ). Sealing seam ( 18 ) has at least one indentation ( 26,28 ) which extends inwards from the outer edge of sealing seam ( 18 ), and whose depth of extension is less than width (B) of sealing seam ( 18 ) at the point of the indentation ( 26,28 ).

The present invention relates to a tear-open seal packaging with apackaging element having an opening and a tear-open film which closesthe opening according to the preamble of claim 1.

Seal packagings of this type are used for food, for example. A containerto accommodate the product is closed with a sealing film made ofaluminium, plastic or a composite material. An impermeable connection iscreated along the sealing seam between the opening edge of the containerand the outer edge of the film, e.g. by melting a sealing coating ontothe underside of the film, or onto the top of the container or packagingelement. In this way, the film and the edge of the packaging enter intoa material-locking connection with each other.

Whilst in many cases, the container is formed as a single moulded part,one may also provide one part of the packaging only with tear-open film,and then connect this part to the rest of the packaging. Such a part maybe an intermediate ring, whose opening is initially seal with thetear-open film, before it is then impermeably connected with anotherpart of the container by means of crimping or some other prior artmethod. Within the meaning of this invention, then, the term packagingelement is understood to designate both entire packagings such as pots,sealed bowls or such like, as well as parts thereof, such as theaforementioned intermediate rings.

Seal packagings must satisfy various requirements. On the one hand, thecontents must be reliably protected. The packaging must, therefore, beimpermeable, stable and resistant to damage. On the other hand, itshould also be easy to open. Meeting both needs simultaneously isproblematic in some cases, especially in terms of the shape and strengthof the sealing seam. Reliable sealing can be achieved by widening thesealing seam, but this makes the film more difficult to tear open. Thesealing seam in the vicinity of any tear-open tab part of the film isespecially critical. As a general rule, this is where, at the start ofthe opening process, the greatest tear-open forces occur, and yet theconsumer is only given a small tab to grip and pull on the film. If anarc-shaped seam is torn open from the exterior, the force required tocontinue tearing open initially increases considerably because thelength of the tear-open edge, i.e. the width of the seal connectionbetween the film and the opening edge of the packaging, is very large atthe outset.

A high tear-open force at the outset of the opening process may causethe already detached part to become torn off from the rest of the film,thereby making it far more difficult, or even impossible, to open thepackaging further, because the consumer can no longer grip the film.Frequently, a hole therefore has to be made in the film with a sharpobject, from where the film can then be pulled off.

When a high tear-open force is applied, the film also frequently tearson one side of the tab, so that the film can then only be partlyremoved, whilst the rest remains seal to the packaging and has to beremoved in a second tear-open operation.

Various proposals have therefore been made to contrive the sealing seamin such a way that the tear-open force is reduced, especially at theoutset of the opening process. The seam can, for example, have atapering or wave-shaped section in the vicinity of the tab, therebydeparting from the arc-shaped path of the seam. This does, however,weaken the seam on the inside. This is a problem, particularly inpackagings which have to withstand high interior pressure. At pointswhere the path of the seam is not curved, i.e. where it zig-zags, stresspeaks may occur if the tear-open film bulges towards the outside, andsaid peaks may destroy the seam, causing impermeability. The path of theseam on such packagings should therefore be as curved as possible inorder to distribute the occurring inner pressure forces as evenly aspossible along the seam. This type of seam path is not compatible withthe use of pre-determined tear-open points in the above-describedmanner.

The task of this invention is, therefore, to create a seal packaging ofthe aforementioned type which is capable of withstanding a relativelyhigh interior pressure and yet can still be easily torn open by theconsumer with a low level of force that is as evenly spread as possible.

This task is solved according to the invention by a tear-open sealpackaging with the features of claim 1.

According to the invention, the sealing seam has at least oneindentation from the exterior, extending inwards from the outer edge ofthe sealing seam. The depth of extension is less than the width of thesealing seam at the location in question.

As a result of the indentation or indentations, the sealing seam isslightly weakened in places from the exterior in such a way that whenthe film is torn open at the point where there is an indentation towardsthe middle of the film, the force is reduced to the level required tobreak the seam connection. The length of the tear-open edge, i.e. thewidth of the seal connection between film and opening edge of thepackaging, is reduced by the indentations as will be explained in moredetail further on in the description. As the depth of extension of theindentations is less than the width of the seam, the sealing seam is notweakened from its inner edge and is capable of withstanding even highdegrees of stress such as those which may be caused by high pressure onthe inside of the seal packaging.

In particular, such indentations can be applied without difficulty tocurved sealing seams.

In the context of this invention, the term “indentation” designates arecess of any shape in the outer edge of the sealing seam, without theshape of said recess being specified. The person skilled in the art mayadapt the shape, width and depth of this recess in suitable manner tothe respective requirements of the seal packaging.

The indentation or indentations are preferably disposed on anapproximately circular-shaped section of the sealing seam.

The indentation(s) is/are preferably disposed in a portion between animaginary tangent of the outer edge of the sealing seam and a parallelimaginary tangent of the inner edge of the sealing seam.

Further, the indentation(s) is/are preferably shaped as a recess with anarc-shaped edge.

In a preferred form of embodiment, the tear-open film is provided with afree tear-open tab along an edge portion at an indentation in thesealing seam.

The sealing seam preferably has at least two indentations at a distancefrom each other along the sealing seam.

In this case, the tab can preferably be disposed between twoindentations.

Pulling on the tab thus produces a tear-open edge which extends betweenthe indentations and is shortened at both ends by the latter. Thisdecisively reduces the material resistance, and hence the tensile forcerequired to continue pulling the tab back further.

According to another preferred form of embodiment, recesses are disposedat opposite points on the sealing seam.

Whilst the tear-open film can be torn open at a point at which there arenotches to reduce the required tear-open force, in this form ofembodiment opposite indentations additionally ensure that the process offully detaching the film from the opening edge proceeds evenly, ratherthan causing, here too, a sudden increase in the level of forcerequired.

In one preferred form of embodiment, the packaging element is anintermediate ring which forms the upper edge of a container and ismechanically or materially connected to the other part of the container.

A preferred example of an embodiment will be described in more detailbelow with reference to the drawings, in which

FIG. 1 is a top-plan view of an embodiment of the tear-open sealpackaging according to the invention;

FIG. 2 is a view of parts of the seal packaging as seen in FIG. 1,before being joined together;

FIG. 3 shows the parts of the seal packaging as seen in FIG. 2, duringjoining-up;

FIG. 4 is a section through the seal packaging as seen in FIG. 1;

FIG. 5 shows the sealing seam of the seal packaging as seen in FIG. 1 to4;

FIG. 6 to 8 show a perspective view of a conventional seal packaging asper FIG. 1, during the tear-open process;

FIG. 9 shows the seal packaging according to the invention, in atear-open position as per FIG. 7; and

FIG. 10 is a force-path diagram to illustrate the forces during thetear-open process.

The tear-open seal packaging 10 shown in FIG. 1 comprises a ring-shapedpackaging element 12, namely an intermediate ring forming the top edgeof a packaging. The ring opening is sealed by a tear-open film 14 withan essentially circular peripheral edge 16. To this end, the outer edgeportion 16 of tear-open film 14 is connected to the opening edge ofpackaging element 12 by a circular-shaped sealing seam 18. This sealingseam 18 is created, for example, by melting a meltable coating onto theunderside of tear-open film 14 by means of a stamp tool, so thattear-open film 14 and packaging element 12 enter into a material-lockingconnection with each other. Sealing seam 18 can therefore be createdunder the action of heat. Another means of connection, such as adhesion,could conceivably also be used.

Along the edge portion disposed uppermost in FIG. 1, tear-open film 14is provided with a free tear-open tab 20. This tear-open tab 20 liesfolded on the top side of tear-open film 14 and can be finger-gripped bythe user of seal packaging 10. By pulling on tear-open tab 20, tear-openfilm 14 can be torn open, thereby exposing the opening of packagingelement 12.

In this figure, the path of sealing seam 18 (not visible in the top-planview shown in FIG. 1) underneath the edge 16 of tear-open film 14 isdiagrammatically illustrated by hatching. The inner edge 22 of sealingseam 18 is circular. Along its outer edge 24, sealing seam 18 has anindentation 26,28 on each side of tear-open tab 20. Indentations 26,28are thus distanced from each other along sealing seam 18, and extendinwards from the outer edge 24 of sealing seam 18. The depth of thisextension is less than the width of sealing seam 18 between its inneredge 22 and outer edge 24. Thus sealing seam 18 is not completely brokenby indentations 26,28, but rather the seal remains intact from theinside. As will be explained in more detail below, indentations 26,28make it easier to tear open tear-open film 14 by pulling on tear-opentab 20 disposed between indentations 26,28.

At this point, the manufacturing process used for the seal packaging 10according to the invention will be described. FIG. 2 and 3 show thering-shaped packaging element 12, namely the intermediate ring, with, atits centre, a circular opening 30. The edge 32 of this opening 30 isformed by an inward and downward graduation of the cross-section ofpackaging element 12, i.e. towards the interior of the packaging, whichis not shown. Packaging element 12 can, however, also have a differentcross-section to the one shown in FIG. 3.

The unit shown in FIG. 1, comprising packaging element 12 and tear-openfilm 14, is formed by lowering the punched-out tear-open film 14 ontopackaging element 12, so that the outer edge portion 16 of tear-openfilm 14 rests on the opening edge 32 of packaging element 12, and bymaterial-locking connection of superposed edges 16 and 32, resulting inthe configuration in FIG. 4. The material-locking connection createssealing seam 18, which seals edges 16 and 32 together impermeably. Inparticular, the sealing is impermeable to liquid and/or gas.

As shown in FIG. 2, tear-open film 14 and tear-open tab 20 are contrivedfrom a single blank. Tear-open tab 20 can be folded back onto thecircular surface of tear-open film 14 in a manner not illustrated inmore detail as film 14 is sealed onto packaging element 12.

Edges 16 and 32 can be sealed together with a suitable stamp tool, bymeans of which tear-open film 14 and packaging element 12 are pressedtogether from above and below. The sealing point is heated during thepressing process. Alternatively, the heat required for sealing can besupplied to packaging element 12 before pressing.

The unit shown in FIG. 4, comprising packaging element 12 and tear-openfilm 14, is then connected to a container not shown in more detail, e.g.by crimping the outer edge 34 of packaging element 12 with the top edgeof the container. Alternatively, one may contrive the packaging as onepiece and seal off its opening with a tear-open film 14. Hence the term“packaging element” refers, in the context of this invention, both toparts of the packaging, such as the intermediate ring of this form ofembodiment, as shown in the figures, or to packagings contrived as onepiece.

The shape of the sealing seam is shown in more detail in FIG. 5. Asalready explained in connection with FIG. 1, sealing seam 18 isessentially circular. The width B of sealing seam 18, i.e. the distancebetween its inner edge 22 and its outer edge 24 in the radial directionremains the same around the greater part of its circumference. In oneportion 36 only, which is disposed at the top in FIG. 5, sealing seam 18has two indentations 26,28, which are located at a distance from eachother along the path of sealing seam 18. As already illustrated in FIG.1, the tear-open tab 20 of the tear-open film 14 on seam 18 is disposedin the gap between the two indentations 26,28.

Indentations 26,28 are each contrived as an arc-shaped recess in theouter edge 24 of sealing seam 18. The depth of each recess is less thanthe width B of the sealing seam at the point of each indentation. Thusthe path of sealing seam 18 is never completely broken at any point. Inparticular, the inner edge 22 of sealing seam 18 retains its round shapeand is not touched by indentations 26,28. Indentations 26,28 arerelatively flat, i.e., their width in the circumferential direction issubstantially greater than their depth in the radial direction. Theradii of the arcs of the recess edges of indentations 26,28 are greaterthan the width B of sealing seam 18, i.e. the centre point of these arcs38 lies relatively far outside seam 18.

Indentations 26,28 need not necessarily have the recess shape shownhere, the shape may differ. In particular, flatter, or less flat,indentations 26,28 are also conceivable, as well as V-shaped recesses,etc. The distance between indentations 26,28 may also vary.

The mode of functioning of indentations 26,28 will now be explained inmore detail with reference to the following figures. For the sake ofbetter comprehension, the mode of functioning of a conventional sealpackaging will be described first.

FIGS. 6 to 8 show a top plan view of a conventional seal packaging 110,whose packaging element 112 is contrived like the intermediate ring 12of the seal packaging 10 according to the invention, and whose tear-openfilm 114 has the same shape as tear-open film 14 of seal packaging 10.Tear-open film 114 is also provided with a tear-open tab 120. Runningunderneath the edge portion 116 of tear-open film 114 there is a roundsealing seam 118 to seal tear-open film 114 onto the opening edge ofpackaging element 112. In contrast to sealing seam 18 according to theinvention, the conventional sealing seam 118 is not provided withindentations, i.e. both its inner edge 122 and outer edge 124 arecircular and unbroken, and the width B around the complete periphery ofsealing seam 118 is the same as that of sealing seam 18 according to theinvention.

If one pulls on tear-open tab 120, thereby exerting tensile force F ontab 120 towards the opposite edge area of tear-open film 114, this forceF acts along a line separating the already detached part of tear-openfilm 114 from the surface area of film 114 that is still firmlyconnected to packaging element 112 by means of sealing seam 118, andlies flat on the opening thereof. This line, which will be referred tobelow as separating line 50, runs perpendicular to the direction of pullof tab 120 and corresponds to a chord connecting two points on thecircular outer edge 116 of tear-open film 114. As the pulling movementprogresses, tab 120 grows longer by the detached part of the film assealing seam 118 gives way to tensile force F, and separating line 50moves towards the middle of tear-open film 114, becoming longer as itdoes so.

The amount of force required to pull tab 120 further depends on themomentary material resistance along separating line 50. This in turndepends on the length of the section(s) of separating line 50 runningover sealing seam 118, i.e. via which there is contact with sealing seam118, contact which has to be overcome by exerting tensile force. In FIG.6, tab 120 is partially pulled away from sealing seam 118, but only tothe extent that separating line 50 has not yet moved inwards beyond thefull width B of sealing seam 118. That is, sealing seam 118 is stillintact from the inside of the sealing packaging, and the opening isstill closed. Separating line 50 therefore cuts through two points 52and 54 on the outer edge 124 of sealing seam 118, but not inner edge122. The required tensile force F is thus determined by the length L1 ofa tear-open edge 56 between these points 52 and 54, which is onlyslightly shorter than the entire length of separating line 50. Tear-openedge 56 corresponds to a chord connecting the two points 52,54 on thearc of the outer edge 124 of sealing seam 118.

As can be seen in FIG. 7, separating line 50 lengthens as tab 120 ispulled further, as does tear-open edge 56, as the latter moves radiallyinward together with separating line 50, and the chord between points 52and 54 on the outer edge 124 of sealing seam 118 becomes longer. Thetensile force F required for tearing open also increases as thishappens. This is clearly illustrated in the force-path diagram in FIG.10. The section of curve designated by a 1 in a circle indicates theposition in FIG. 6, the maximum in position 2 equates with FIG. 7, etc.The curve increases sharply on the way from the not yet torn-openposition in which sealing seam 118 is still intact, to the position inFIG. 7, in which separating line 50 touches the inner edge 122 ofsealing seam 118. As tearing-open proceeds, separating line 50 movesbeyond inner edge 122 of sealing seam 118 (see FIG. 8). As a result,only the end portions of separating line 50 remain in contact withsealing seam 118. The contact is reduced to two narrow tear-open edges58,60, which cut through sealing seam 118 at two points around thecircumference positioned at a distance from each other. As tab 120 ispulled back further, tear-open edges 58,60 move, together withseparating line 50, further along sealing seam 118, withoutsubstantially changing in length. Thus the force F required for tearingopen is hardly any greater, as the flat section of curve clearly showsin FIG. 10 (position 3).

The above description reveals that the force, F, required for tearingopen, increases with the length L1 of tear-open edge 56. The maximumforce occurs in the situation in FIG. 7, in which length L1 of tear-openedge 56 is at its maximum, and sealing seam 118 offers the greatestamount of material resistance.

The way in which the present invention considerably reduces this forcepeak, thereby substantially facilitating the process of opening sealpackaging 10, will be described below.

FIG. 9 shows the seal packaging 10 with the sealing seam 18 of FIG. 5,provided with the two indentations 26,28. The situation in FIG. 9coincides with that in FIG. 7, in which separating line 50 between thedetached and the still attached part of tear-open film 14 has just gonebeyond the full width B of sealing seam 18 and reached the inner edge 22of seam 18. Note here that tear-open edge 62 is substantially shorterthan tear-open edge 56 in FIG. 7. This is achieved by indentations26,28, past which separating line 50 moves during the pulling openmovement. In the situation shown in FIG. 9, indentations 26,28 shortenthe length of tear-open edge 62 from the lateral ends, and diminish thecontact area with film 14. This lessens the material resistance, and theforce F required for pulling back is less (see path of curve marked 2′in FIG. 10).

Indentations 26,28 are disposed at an angular distance around theperiphery of sealing seam 18 in such a way that separating line 50,which moves inwards during the pulling back movement, parallel to theprogression thereof, passes just beyond indentations 26,28 at the momentat which the inner edge 22 of sealing seam 18 has already been reached,and no further critical force peaks can occur. Hence indentations 26,28are advantageously disposed in a strip-shaped area limited by twoparallel straight lines, of which one straight line is a tangent ofouter edge 24 of sealing seam 18 and the other straight line forms atangent of inner edge 22, which simultaneously forms a secant of outeredge 24.

As can be seen in the force-path diagram in FIG. 10, a further forcepeak can occur at the end of the opening path, just before tear-openfilm 14 is completely torn off, caused by separating line 50 coming intocontact with the opposite inner edge 22 of sealing seam 18. As thishappens, the two tear-open edges 58 and 60 join up to re-become a singletear-open edge with a width as shown in FIG. 7, requiring, once again,application of maximum force. By providing indentations oppositeindentations 26,28 on the side of tear-open tab 20 on sealing seam 18,the width of the tear-open edge can be reduced here too, and hence thetear-open resistance of film 14 as well.

Indentations 26,28 have virtually no weakening impact on sealing seam 18on the inside portion of the opening of seal packaging 10. The inventionis therefore especially well suited for use with seal packagings whichhave to resist a high level of inner pressure, as the pressure force candistribute itself evenly along the circular inner edge 22 of sealingseam 18, and no stresses occur in tear-open film 14. And yet thetear-open process is made considerably easier, and proceeds more evenly,by providing indentations 26,28.

Departing from the embodiment described in connection with the Figures,the desired effect of weakening the material resistance at the tear-openpoint can also be achieved with a single indentation. If, for example,one omits one of the two indentations 26 or 28 of the above-describedembodiment, so that the other indentation remains, tear-open edge 56 isshortened at one end only. The effect of reducing the required tensileforce may be slightly less in this case. The user will still, however,find the process of tearing open the film much easier.

Further, the indentations can of course be contrived in sealing seamsshaped differently to that shown in FIG. 5, and are not circular. Itwould be conceivable, for example, to contrive indentations in anarc-shaped rounded corner in an essentially square sealing seam, or inan oval sealing seam or such like. In this respect, too, theabove-described embodiment deriving from FIGS. 1 to 10 is not limitingfor the invention.

1. Tear-open seal packaging, comprising a packaging element having anopening and a tear-open film, which closes said opening and is connectedalong an outer edge portion thereof with an opening edge of saidpackaging element by a sealing seam, said sealing seam having at leastone indentation which extends inwards from an outer edge of the sealingseam, and the at least one indentation having a depth of extension whichis less than the width of the sealing seam at the point of theindentation.
 2. Seal packaging according to claim 1, wherein at leastone said indentation is disposed on an approximately arc-shaped sectionof the sealing seam.
 3. Seal packaging of claim 1, wherein at least onesaid indentation is disposed in a region between an imaginary tangent ofthe outer edge of the sealing seam and an imaginary parallel tangent ofan inner edge of the sealing seam.
 4. Seal packaging according to claim1, wherein at least one said indentation is shaped like a recess with anarc-shaped edge.
 5. Seal packaging according to claim 1, wherein thetear-open film is provided with a free tear-open tab at one edge portionon one indentation in the sealing seam.
 6. Seal packaging according toclaim 1, wherein at least two said indentations are contrived in thesealing seam, and are located at a distance from each other along thesealing seam.
 7. Seal packaging according to claim 6, wherein thetear-open film is provided with a free tear-open tab at one edge portionon one indentation in the sealing seam and the free tear-open tab isdisposed between two indentations in the sealing seam.
 8. Seal packagingaccording to claim 1, wherein the indentations are disposed at oppositepoints in the sealing seam.
 9. Seal packaging according to claim 1,wherein the packaging element is an intermediate ring which forms a topedge of a container and is connected to another part of the container.